Catheter with soft distal tip for mapping and ablating tubular region

ABSTRACT

A catheter includes an elongated body having a longitudinal axis, a distal assembly distal the elongated body, the distal assembly having a tapered helical form comprising a larger, electrode-carrying proximal loop and a smaller, softer distal loop, and a shape-memory support member extending through at least the proximal loop. For example, the helical loop subtends at least about 720 radial degrees, with the proximal loop subtending about 360 radial degrees, and the distal loop subtending about 360 radial degrees. The softer distal loop with a straight distal end atraumatically guides the distal assembly into a tubular region so that the larger proximal loop can sit on the ostium of the tubular region with improved electrode and tissue contact.

FIELD OF INVENTION

This invention relates generally to methods and devices for invasivemedical treatment, and specifically to catheters, in particular,catheters having distal sections adapted for mapping and ablatingselected anatomy.

BACKGROUND

Ablation of myocardial tissue is well known as a treatment for cardiacarrhythmias. In radio-frequency (RF) ablation, for example a catheter isinserted into the heart and brought into contact with tissue at a targetlocation. RF energy is then applied through an electrode on the catheterin order to create a lesion for the purpose of breaking arrthythmogeniccurrent paths in the tissue.

Recently, circumferential ablation of the ostia of the pulmonary veinhas gained acceptance as a treatment for atrial arrhythmias, andparticularly for atrial fibrillation. For example, U.S. Pat. No.6,064,902, whose disclosure is incorporated herein by reference,describes a catheter for ablating tissue on the inner wall of a bloodvessel, such as a pulmonary vein. The tip portion of the catheter isdeflectable from a first, generally straight, configuration, in whichthe proximal and distal sections are substantially co-linear, to asecond, J-shaped, configuration in which the proximal and distalsections are generally parallel with a separation therebetweensubstantially corresponding to the inside diameter of the blood vessel.The distal end portion of the catheter is rotated about the longitudinalaxis of the catheter to cause a circumferential displacement of proximaland distal ablation electrodes on the catheter along the inner wall ofthe pulmonary vein. In this way, the electrode catheter may be used toablate a number of circumferentially-spaced sites on the inner wall ofthe pulmonary vein by ablating one or two sites at each circumferentialposition.

U.S. Patent Application Publication 2005/0033135, whose disclosure isincorporated herein by reference, describes a lasso for pulmonary veinmapping and ablation. A catheter for circumferentially mapping apulmonary vein (PV) includes a curved section shaped to generallyconform to the shape of the interior surface of the PV. The curvedsection is connected to catheter by a generally straight axial basesection that is in an “on edge” configuration where the base axialsection connects to the curved section on the circumference of thecurved section. The curved section comprises one or more sensingelectrodes, and its proximal end is joined at a fixed or generally knownangle to a base section of the catheter. Position sensors are fixed tothe curved section of the catheter and to the distal end of the basesection. The catheter is inserted into the heart, and the curved sectionis positioned in contact with the wall of the PV, while the base sectionremains within the left atrium, typically positioned such that the jointwith the curved section is at the ostium of the vein. The informationgenerated by the three position sensors is used to calculate thelocations and orientations of the sensing electrodes, which enablesmapping of the surface of the PV. The sensing electrodes mayadditionally perform ablation of selected sites, or the catheter mayfurther comprise ablation elements.

U.S. Pat. No. 7,008,401, whose disclosure is incorporated herein byreference, describes compound steering assemblies, usable in bothdiagnostic and therapeutic applications, for steering the distal sectionof a catheter in multiple planes or complex curves. These assemblies aresaid to enable a physician to swiftly and accurately position andmaintain ablation and/or mapping electrodes in intimate contact with aninterior body surface. U.S. Pat. No. 5,820,591, whose disclosure isincorporated herein by reference, similarly describes compound steeringassemblies of this sort.

U.S. Pat. No. 8,608,735, issued on Dec. 17, 2013, whose disclosure isincorporated herein by reference, describes a medical device, includingan insertion shaft, having a longitudinal axis and having a distal endadapted for insertion into a body of a patient. A resilient end sectionis fixed to the distal end of the insertion shaft and is formed so as todefine, when unconstrained, an arc oriented obliquely relative to theaxis and having a center of curvature on the axis. One or moreelectrodes are disposed at respective locations along the end section.

However, because human anatomy varies between individuals, the shape andsize of an ostium vary, and the end section whether having an arcuateshape or a generally circular shape may not always fit the particulartarget ostium. Moreover, because the right atrium is a confined volume,the approach into a PV ostium is often times indirect in that the distalsection does not always assume a perpendicular angle to the target site.Because of these factors, contact between the electrodes and the ostiumis often less than complete. If pressure is applied in the axialdirection to the distal section in an attempt to improve electrodecontact with the ostium, and/or if the catheter is rotated about itslongitudinal axis, the distal section may slip off the ostium.

Accordingly, a desire exists for a lasso-type catheter that can providea distal section whose curved (or circular, used interchangeably herein)portion can be inserted atraumatically into a tubular region, such as apulmonary vein, to ensure placement accuracy of the electrodes at theostium of the pulmonary vein and minimize the risk of the curved portiondislodging from the ostium when increased pressure is applied or thecurved portion is rotated about the ostium.

SUMMARY OF THE INVENTION

The present invention is directed to a steerable, multi-electrode,irrigated, luminal catheter that is particularly useful for deploymentin the atria of the heart through a guiding sheath. The catheter isconfigured to facilitate electrophysiological mapping of the atria andto transmit radiofrequency (RF) current to the catheter electrodes forablation purposes. The catheter includes an arcuate resilient distalassembly, wherein the distal assembly has a tapered helical formincluding a larger proximal loop and a smaller distal loop adapted foruse in a tubular region. Whereas the distal loop has a smaller radius, asofter structure with a greater flexibility, and a softer straightdistal end section that helps guide the distal loop into the tubularregion, the proximal loop has a stiffer structure and a larger radius toensure contact between its electrodes and the ostium of the tubularregion. The softer straight distal end section provides an atraumaticleading element that guides the distal loop into the tubular region andensures placement accuracy of the proximal loop, especially when anaxial force is applied by the user.

The centered, tapered helical form of the distal assembly allows forimproved tissue contact and annular motion. The helical form has apredetermined pitch that provides gentle pressure to ensure contact ofthe electrodes in the distal assembly with the ostium. The taperedhelical form ensures that the distal loop can fit into the tubularregion which in turn ensures placement accuracy of the proximal loop andablation electrodes thereon on the ostium.

The pitch of the helical form can be varied along the length of thehelical form. For example, the pitch of the proximal loop can be greaterthan the pitch of the distal loop. Alternatively, both the pitch and theradius of helical form can be varied along the length of the helicalform.

In some embodiments, the catheter includes an elongated body having alongitudinal axis, a distal assembly distal the elongated body, thedistal assembly having a helical form comprising a proximal loop and adistal loop, and a shape-memory support member extending through atleast the proximal loop. The catheter also includes at least oneirrigated ablation ring electrode mounted on the proximal loop, and acontrol handle proximal the elongated body, wherein the proximal loophas a lesser flexibility and the distal loop has a greater flexibility.

In some detailed embodiments, the helical form subtends at least about720 radial degrees, with the proximal loop subtending about 360 radialdegrees, and the distal loop subtending about 360 radial degrees.

In some detailed embodiments, the helical form is on axis relative to alongitudinal axis of the catheter. A generally straight distal endextends distally from the distal loop which is also on-axis relative tothe longitudinal axis.

In some detailed embodiments, the helical form is tapered, wherein theproximal loop has a greater radius and the distal loop has a lesserradius.

In some detailed embodiments, the proximal loop and the distal loop areoriented obliquely at an angle relative to a longitudinal axis of thecatheter. In some more detailed embodiments, the oblique angle rangesbetween about 45 degrees to 105 degrees, preferably between about 75 to105 degrees, and more preferably the oblique angle is about 90 degrees.

In some embodiments, the proximal loop includes between about eight totwenty electrodes, and preferably about ten electrodes, which subtendabout 360 radial degrees. Alternatively, the proximal loop includesabout six electrodes which subtend about 180 radial degrees.

In some detailed embodiments, the distal loop includes ring electrodesfor sensing electrical potentials.

The catheter may also comprise a contraction wire extending through theelongated body and the distal assembly, wherein the control handleincludes a first control member configured to actuate the contractionwire to contract the helical form.

The catheter may also further comprise a deflection wire extendingthrough the elongated body, wherein the control handle includes a secondcontrol member configured to actuate the deflection wire to deflect aportion of the elongated body.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention will bebetter understood by reference to the following detailed descriptionwhen considered in conjunction with the accompanying drawings. It isunderstood that selected structures and features have not been shown incertain drawings so as to provide better viewing of the remainingstructures and features.

FIG. 1 is a top plan view of a catheter of the present invention, inaccordance with some embodiments.

FIG. 2 is a detailed view of a distal assembly of the catheter of FIG.1.

FIG. 2A is a cross-sectional view of the distal assembly of FIG. 2,taken along line C-C.

FIG. 3 is an end view of the distal assembly of FIG. 2.

FIG. 4A is a side view of a distal assembly approaching an ostium,according to some embodiments of the present invention.

FIG. 4B is a side view of the distal assembly of FIG. 4A in contact withthe ostium.

FIG. 5A is a side cross-sectional view of the catheter of FIG. 1, takenalong line K-K at a junction between a catheter body and an intermediatedeflection section, along a first diameter.

FIG. 5B is a side cross-sectional view of the junction of FIG. 5A, alonga second diameter generally perpendicular to the first diameter.

FIG. 6 is an end cross-sectional view of the catheter of FIG. 1, takenalong line H-H.

FIG. 7 is a side cross-sectional view of the catheter of FIG. 1, takenalong line E-E at a junction between the intermediate deflection sectionand the distal assembly.

FIG. 8 is a side cross-sectional view of a junction between a proximalloop and a distal loop of the distal assembly of the catheter of FIG. 1.

FIG. 9 is a perspective view of an embodiment of an irrigated ablationelectrode.

FIG. 10 is a side cross-sectional view of a portion a proximal loop andan irrigated ablation electrode mounted thereon of the catheter of FIG.1.

FIG. 11 is a detailed perspective view of a distal assembly, inaccordance with another embodiment of the present invention.

FIG. 12 is a side cross-sectional view of the control handle of FIG. 1,taken along line L-L.

FIG. 13 is a partial detailed view of the control handle of FIG. 12.

FIG. 14 is a schematic pictorial illustration of a system for ablationof tissue in the heart, in accordance with an embodiment of the presentinvention.

FIG. 15 is a schematic sectional view of a heart showing insertion of acatheter into the left atrium, in accordance with an embodiment of thepresent invention.

FIG. 16 is a detailed perspective view of a distal assembly, inaccordance with yet another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Lasso catheters, as described above, may be used for mapping andablating tissue along an arc or curve surrounding an anatomicalstructure, such as the ostium of a pulmonary vein. The lasso isgenerally made thin and flexible, for purposes of maneuverability, withlarge ring electrodes to minimize electrical resistance. U.S. Pat. No.8,475,450, issued Jul. 2, 2013, entitled DUAL-PURPOSE LASSO CATHETERWITH IRRIGATION, which is assigned to the assignee of the present patentapplication and whose disclosure is incorporated herein by reference,describes an alternative design in which the lasso is thicker andstiffer. U.S. patent application Ser. No. 13/174,742, filed Jun. 30,2011 (now published as 2013/0006238), which is assigned to the assigneeof the present patent application and whose disclosure is incorporatedherein by reference, describes a lasso catheter whose distal assemblyhas a curved configuration that can be varied by means of a contractionwire actuated by a control handle.

Embodiments of the present invention that are described hereinbelowprovide probes, such as catheters, with improved lasso-type structuresto facilitate maneuvering and positioning in the heart. Such catheterscan be used to produce curved, circular, looped or otherwise closedablation paths, as well as sensing electrical activity along a curve,circle, loop or closed pattern for electrical potential and anatomicalmapping.

Referring to FIGS. 1 and 2, a catheter 10 according to the disclosedembodiments comprises an elongated body that may include an insertionshaft or catheter body 12 having a longitudinal axis, and anintermediate section 14 distal of the catheter body that can be uni- orbi-directionally deflected off axis from the catheter body longitudinalaxis. A resilient three-dimensional distal assembly 17, with ringelectrodes 19 disposed along a nonlinear or curved distal portion,extends from the elongated body 12 or the intermediate section 14. Inaccordance with a feature of the present invention, the curved distalportion 17 defines, when unconstrained, a generally helical form 22. Thehelical form is oriented obliquely relative to a longitudinal axis 25 ofthe catheter 10 extending from the intermediate section 14. The term“obliquely”, in the context of the present invention means that theplane P in space that best fits the helical form is angled relative tothe longitudinal axis 25. An angle θ between the plane P and the axis 25ranges between about 45 to 105 degrees, preferably between about 75 to105 degrees, and more preferably about 90 degrees. Moreover, the helicalform 22 of the distal assembly 17 spirals or subtends in a predeterminedmanner. The helical form 22 of the distal assembly 17 is advantageouslycentered or on-axis relative to the longitudinal axis 25 and is taperedfor improved tissue contact and annular motion, as best seen in FIG. 3.

The distal assembly 17 has an electrode-carrying proximal loop 17P, anda soft “pigtail” that includes a distal loop 17D and a distal straightend section 17E, wherein the distal′ loop 17D and the distal straightend section 17E have a greater resiliency than the resiliency of theelectrode-carrying proximal loop 17P. The pitch of the helical form 22of the distal assembly 17 is selected to provide a gentle pressure forensuring contact of all of ring electrodes 19 with tissue. As shown inFIGS. 4A and 4B, tapering of the helical form 22 ensures that thesmaller distal loop 17D can fit into the tubular region or pulmonaryvein which ensures placement of accuracy of the larger proximal loop 17Pand the ring electrodes 19 carried thereon at an ostium 11 of thetubular region 13, e.g., a pulmonary vein. The greater flexibility ofthe distal loop 17D and the distal straight end section 17E provides anatraumatic leading element that guides distal assembly 17 into thetubular region or pulmonary vein and ensures placement accuracy of thedistal assembly.

The catheter enters a patient's body through a guiding sheath that hasbeen inserted in a body cavity, such as a heart chamber. Due to theflexible construction of the distal assembly 17, the helical form 22readily straightens for insertion into the guiding sheath. The distalassembly is advanced axially in the guiding sheath until it moves pastthe distal end of the guiding sheath toward a tissue in the body, suchas the inner heart wall. (The term “axial” refers to the direction alongor parallel to the longitudinal axis of the catheter). When exposed andunconstrained, the distal assembly 17 reassumes the helical form 22which is maneuvered to engage the tissue surface frontally with some orall of the ring electrodes 19 on the proximal loop 17P contacting thetissue surface simultaneously, as shown in FIGS. 4A and 4B. Inaccordance with the present invention, the straight distal end section17E facilitates entry of the distal loop 17D into a tubular region byguiding the helical form 22 into the tubular region, whereupon thedistal loop 17D is placed deeper into the tubular region to stabilizethe placement of the proximal loop 17P and ring electrodes 19 on theostium. The “softness” or resiliency of the distal loop 17P and thestraight distal end section 17E renders these structures atraumatic soas to minimize the risk of tissue damage from any axial misalignmentwith the tubular region as these structures enter the tubular region.Moreover, as a user applies axial force to the catheter to push thedistal assembly 17 against the ostium for better tissue contact, thedistal loop 17P and the distal end section 17E positioned deeper in thetubular region minimize the risk of the proximal loop 17P slipping offthe ostium, especially where the approach or the placement of the distalassembly 17 is off angle and not directly “head-on.” As discussed indetail further below, if the ostium is smaller in diameter than theproximal loop 17P in its natural relaxed state, the operator cancontract the proximal loop 17P by means of a contraction wiremanipulated via the control handle.

In the depicted embodiment of FIGS. 5A and 5B, the catheter body 12comprises an elongated tubular construction having a single, axial orcentral lumen 18. The catheter body 12 is flexible, i.e., bendable, butsubstantially non-compressible along its length. The catheter body 12can be of any suitable construction and made of any suitable material. Apresently preferred construction comprises an outer wall 30 made ofpolyurethane or PEBAX. The outer wall 30 comprises an imbedded braidedmesh of stainless steel or the like, as is generally known in the art,to increase torsional stiffness of the catheter body 12 so that, whenthe control handle 16 is rotated, the intermediate section 14 and distalassembly 17 will rotate in a corresponding manner.

The outer diameter of the catheter body 12 is not critical, but ispreferably no more than about 8 french, more preferably 7 french.Likewise the thickness of the outer wall 30 is not critical, but is thinenough so that the central lumen 18 can accommodate any desired wires,cables and/or tubes. The inner surface of the outer wall 30 is linedwith a stiffening tube 31 to provide improved torsional stability. Theouter diameter of the stiffening tube 31 is about the same as orslightly smaller than the inner diameter of the outer wall 30. Thestiffening tube 31 can be made of any suitable material, such aspolyimide, which provides very good stiffness and does not soften atbody temperature.

The deflectable intermediate section 14 comprises a short section oftubing 15 having multiple lumens, each occupied by the variouscomponents extending through the intermediate section. In theillustrated embodiment of FIG. 6, there are six lumens. Leadwire/thermocouple pairs 40, 41 for each ring electrode pass through afirst lumen 33. A nonconductive protective sheath 42 may be provided.Irrigation tubing 43 for delivering irrigation fluid to the distalassembly 17 passes through a second lumen 34. A contraction wire 44passes through a third lumen 35. A cable 46 for a location sensorassembly 48, including a plurality of single axis sensors (SAS)positioned on the distal assembly 17, passes through a fourth lumen 36.For the distal assembly 17, a shape-memory support member 50 surroundedby a nonconductive tubing 52, e.g., a polyimide tubing, extendsproximally from the distal assembly 17 for a relatively short distanceinto a fifth lumen 37. A puller wire 54 for deflecting the intermediatesection 14 passes through a sixth lumen 38.

The multi-lumened tubing 15 of the intermediate section 14 is made of asuitable non-toxic material that is preferably more flexible than thecatheter body 12. A suitable material is braided polyurethane or PEBAX,i.e., polyurethane or PEBAX with an embedded mesh of braided stainlesssteel or the like. The plurality and size of each lumen are notcritical, provided there is sufficient room to house the componentsextending therethrough. Position of each lumen is also not critical,except the position of the third lumen 35 for the distal assemblycontraction wire 44 is preferably more aligned with an innercircumference of the proximal loop 17P of the distal assembly 17 so thatproximal movement of the wire can readily contract the proximal loop17P. Moreover, the sixth lumen 38 for the deflection wire 54 is off-axisso that distal movement of the deflection wire relative to the catheteraccomplishes deflection toward the side on which lumen is off axis.Preferably, the third and sixth lumens 35 and 38 are diametricallyopposed to each other.

The useful length of the catheter, i.e., that portion that can beinserted into the patient's body excluding the distal assembly 17, canvary as desired. Preferably the useful length ranges from about 110 cmto about 120 cm. The length of the intermediate section 14 is arelatively small portion of the useful length, and preferably rangesfrom about 3.5 cm to about 10 cm, more preferably from about 5 cm toabout 6.5 cm.

A means for attaching the catheter body 12 to the intermediate section14 is illustrated in FIGS. 5A and 5B. The proximal end of theintermediate section 14 comprises an inner circumferential notch thatreceives the outer surface of the stiffening tube 31 of the catheterbody 12. The intermediate section 14 and catheter body 12 are attachedby glue or the like, for example, polyurethane. If desired, a spacer(not shown) can be provided within the catheter body 12 between thedistal end of the stiffening tube 31 and the proximal end of theintermediate section 14 to provide a transition in flexibility at thejunction of the catheter body 12 and the intermediate section, whichallows the junction to bend smoothly without folding or kinking. Anexample of such a spacer is described in more detail in U.S. Pat. No.5,964,757, the disclosure of which is incorporated herein by reference.

Distal the intermediate section 14 is the distal assembly 17. As shownin FIGS. 2 and 3, the distal assembly 17 includes an angled elbowsection 20 immediately distal of the distal end of the intermediatesection 14 and a transverse curved section 21 that form a proximalportion of the helical form 22. The elbow section 20 has an angle β ofabout 90 degrees and the transverse curved section 21 subtends an angleα of about 135 degrees in the radial direction and an angle θ of about105 degrees from the longitudinal axis 25. These structures and anglesenable the helical form 22 of the distal assembly 17 to be axiallycentered (“on axis”) and obliquely angled relative to the longitudinalaxis 25. The helical form 22 is therefore mounted on the catheter in an“off-edge” configuration, where longitudinal axis 25 of the intermediatesection 14 does not intersect the circumference of the helical form 22but rather extends through the interior of the helical form 22, as bestshown in FIG. 3. In accordance with a feature of the present invention,the helical form 22 of the distal assembly 17 is tapered along itslength by spiraling inwardly with a decreasing radius from its proximalend to its distal end, also best shown in FIG. 3.

With reference to FIGS. 2 and 3, the helical form 22 of the distalassembly 17, in some embodiments, subtends about at least about 720degrees and preferably about 765 degrees. The proximal loop 17P subtendsfrom the distal end of the curved section 21 at least 360 degrees, andpreferably about 405 degrees, and the distal loop 17D subtends from thedistal end of the proximal loop 17P at least about another 360 degreesbefore its distal end 17DD curves sharply inwardly toward thelongitudinal axis 25 and is joined by the distal straight end section17E which is on-axis with the longitudinal axis 25.

The helical form 22 can be defined by a radius r and a pitch P (numberof 360 degreed turns per unit length along its longitudinal axis 25).The diameter suitable for mapping or ablating a PV ostium can rangebetween about 20 mm and 35 mm. The pitch can range between about 0.5″(one 360 degree turn per 0.5 inch) and 0.3″ (one 360 degree turn per 0.3inch). With the helical form 22 tapering from its proximal end to itsdistal end, the radius decreases from RP its proximal end to its distalend RD (wherein RP>RD). The pitch P may remain constant between theproximal end and the distal end of the helical form, or the pitch mayvary therebetween, with a greater pitch in the proximal loop 17P and alesser pitch in the distal loop 17D, or vice versa, as needed ordesired. It is understood that the helical form 22 may curve or spiralin the clockwise or counterclockwise direction. In some embodiments, theproximal loop 17P has an outer diameter OD preferably ranging to about33 mm to about 35 mm. The elbow section 20 has an exposed length rangingbetween about 4 mm and 6 mm and preferably of about 5 mm. The curvedtransverse section 21 has an exposed length ranging between about 5 mmand 7 mm, and preferably of about 6 mm. The helical form 22 from aproximal end of the proximal loop 17P (angle α=0) to a distal end of thestraight distal end section 17E has an exposed length ranging betweenabout 18 mm and 22 mm, and preferably about 20 mm.

The elbow section 20, the curved section 21 and the proximal loop 17P ofthe distal assembly 17 are formed of multi-lumened tubing 56 which canbe preformed with a desirable shape, including the helical form, asunderstood by one of ordinary skill in the art. A means for attachingthe tubing 56 to the tubing 15 of the intermediate section 14 is shownin FIG. 7. An outer circumferential notch is made at the proximal end ofthe tubing 56 which is received in the distal end of the tubing 15.

In the illustrated embodiment of FIG. 2A, the tubing 56 has fouroff-axis lumens, namely, a first lumen 57 for the cable 46 and the SAS48, a second lumen 58 for the ring electrode wire pairs 40, 41, a thirdlumen 59 for irrigation fluid, and a fourth lumen 60 for the supportmember 50 and the contraction wire 44. Again, position and sizing of thelumens is not critical, except the position of the fourth lumen 60 forthe contraction wire 44 is preferably on an inner circumference of theproximal loop 17P so that proximal movement of the wire 44 can readilycontract the proximal loop. The tubing 56 can be made of any suitablematerial, and is preferably made of a biocompatible plastic such aspolyurethane or PEBAX.

In the depicted embodiment, the pre-formed support or spine member 50 ofthe distal assembly 17 extends through the fourth lumen 60 of the tubing56 to define the shape of the helical form 22. The support member 50 ismade of a material having shape-memory, i.e., that can be straightenedor bent out of its original shape upon exertion of a force and iscapable of substantially returning to its original shape upon removal ofthe force. A particularly preferred material for the support member 50is a nickel/titanium alloy. Such alloys typically comprise about 55%nickel and 45% titanium, but may comprise from about 54% to about 57%nickel with the balance being titanium. A preferred nickel/titaniumalloy is Nitinol, which has excellent shape memory, together withductility, strength, corrosion resistance, electrical resistivity andtemperature stability.

The support member 50 has a cross-section of a predetermined shape thatmay be generally circular or generally rectangular, including a squareshape. It is understood that a generally rectangular cross section canprovide greater stiffness compared to a circular cross-section of acomparable size. Moreover, the support member can have a varyingthickness along its length, for example, being thinner distally andthicker proximally so that a distal portion can be more readilycontracted and a proximal portion can better withstand the load from anaxial force that is applied when the distal assembly 17 comes intocontact with target tissue.

In some embodiments, the support member 50 has a proximal end positionedjust proximal of the junction between the intermediate section 14 andthe elbow section 20, for example, about 2-3 mm proximal of the junctionin the fifth lumen 37. Alternatively, the support member 50 can extendfurther proximally into the intermediate section 14, the catheter body12 via the central lumen 18, or further into the control handle 16, asdesired or appropriate. In either instance, a nonconductive protectivetubing 62 (e.g., a braided polyimide tubing) is provided in surroundingrelationship with the support member 50 along its length.

In some embodiments, the support member 50 has a distal end generallycoterminous with the distal end of the proximal loop 17P. In anotherembodiment, as discussed further below, the support member 50 extendsdistally, at least into the distal loop 17D, if not also and thestraight distal end section 17E and has a distal end generallycoterminous with the distal tip of the distal end section 17E.

The contraction wire 44 is provided to contract the proximal loop 17P toreduce its diameter. The contraction wire 44 has a proximal end anchoredin the control handle 16, which is used to manipulate the contractionwire. The contraction wire 44 extends through the central lumen 18 ofthe catheter body 12, the third lumen 35 of the intermediate section 14,the central lumen of the elbow section 20 and the curved transversesection 21, and the fourth lumen 60 of the proximal loop 17P to itsdistal end. In the fourth lumen 60 of the proximal loop 17P, thecontraction wire 44 extends through the nonconductive protective tubing62 along with the support member 50. As mentioned, the fourth lumen 60of the proximal loop 17P is positioned on the side of the proximal loop17P closer to its center. With this arrangement, contraction of theproximal loop 17P is dramatically improved over arrangements where theposition of the contraction wire 44 is not so controlled.

In some embodiments, the nonconductive protective tubing 62 comprisesthree layers, including an inner layer of polyimide over which a braidedlayer is formed, the braided layer comprising a braided stainless steelmesh or the like, as is generally known in the art. The braided layerenhances the strength of the tubing, reducing the tendency for thecontraction wire 44 to straighten the preformed curve of the proximalloop 17P. A thin plastic layer of polytetrafluoroethylene is providedover the braided layer to protect the braided layer. The plastic tube 62has a proximal end anchored to the distal end of the intermediatesection 14.

The support member 50 and the contraction wire 44 extend through theprotective tubing 62. In the illustrated embodiment of FIG. 8, thedistal ends of the support member 50 and the contraction wire 44(anchored in a crimped ferrule 51) are soldered or otherwise attached toa small stainless steel tube 63 which is affixed to the distal end ofthe fourth lumen 60 of the tubing 56 by adhesive. With this arrangement,the relative positions of the contraction wire 44 and the support member50 can be controlled so that the contraction wire 44 can be positionedon the inner side of the proximal loop 17P closer to the center of theproximal loop 17P, as described above. The contraction wire 44 on theinside of the curve pulls the support member 50 to the inside of thecurve, enhancing contraction of the helical form. Further, when theprotective tubing 62 includes a braided layer, it minimizes the risk ofthe contraction wire 44 tearing through the multi-lumen tubing 56 of theproximal loop 17P

With reference to FIG. 8, the distal loop 17D and distal straight endsection 17E include nonconductive outer covering or tubing 82. Thetubing provides a lumen 85 through which the support member 50 extendsat least a short distance, e.g., about 10 mm, distally into the distalloop 17D to help secure the distal loop 17D to the proximal loop 17P. Inother embodiments, the support member 50 may extend further into thedistal loop 17D or even further into the distal end section 17E toprovide their respective helical and straight shapes. It is understoodthat the tubing 82 may also be preformed, e.g., by heating, so that itcan assume the helical and straight shapes without the support member 50extending therethrough. In the illustrated embodiment, the tubing 82 hasa smaller size or french than the tubing 56 for the proximal loop 17P. Ameans for attaching the tubing 82D of the distal loop 17D to the distalend of the proximal loop 17P is shown in FIG. 8. A proximal end of thetubing 82 is received in a trepanned distal end of the tubing 56, and asealant 83, such as polyurethane, is applied to the distal end to form ajunction that seals the lumens of the tubing 56 at its distal end andattaches the tubing 82D to the tubing 56.

The tubing 56 of the proximal loop 17P and the tubing 82 of the distalloop 17D may be made of any suitable material, for example, polyurethaneor PBEXA. In accordance with a feature of the present invention, thematerial of the tubing 56 has a durometer that is equal or greater thanthe durometer of the material of the tubing 82, so that the distal loop17D is softer and has greater resiliency than the proximal loop 17P evenif the support member 50 extending through the proximal loop 17P alsoextends the entirety of distal loop 17D.

With reference to FIGS. 5A and 5B, the compression coil 45 surroundingthe contraction wire 44 extends from the proximal end of the catheterbody 12 and through the third lumen 35 of the intermediate section 14.The compression coil has a distal end at or near the distal end of theintermediate section 14. The compression coil 45 is made of any suitablemetal, preferably stainless steel, and is tightly wound on itself toprovide flexibility, i.e., bending, but to resist compression. The innerdiameter of the compression coil is preferably slightly larger than thediameter of the contraction wire 44. The outer surface of thecompression coil is covered by a flexible, non-conductive sheath, e.g.,made of polyimide tubing. The compression coil preferably is formed of awire having a square or rectangular cross-sectional area, which makes itless compressible than a compression coil formed from a wire having acircular cross-sectional area. As a result, the compression coil 45keeps the catheter body 12, and particularly the intermediate section14, from deflecting when the contraction wire 44 is manipulated tocontract the distal assembly 17 as it absorbs more of the compression.

A plurality of ring electrodes 19 are mounted on predetermined locationson the proximal loop 17P, as shown in FIG. 2. The electrodes can be madeof any suitable solid conductive material, such as platinum or gold,preferably a combination of platinum and iridium or gold and platinum,and mounted onto the tubing with glue or the like. A suitable embodimentof an electrode adapted for ablation and irrigation is illustrated inFIGS. 9 and 10. The ablation reservoir (“AR”) electrode is generallycylindrical with a length greater than its diameter. In someembodiments, the length is about 3.0 mm, the outer diameter is about 2.8mm, and the inner diameter is about 2.33 mm.

In the illustrated embodiment, the AR electrode has a side cross-sectionthat can resemble a barrel with a side wall 65 (with a width, in someembodiments, of about 2.5 mm) that bulges radially such that a midportion diameter MD is greater than end diameter ED at opposing endportions 66. Curved transitional regions 67 are provided between theside wall 65 and the end portions 66 to provide an atraumatic profilewithout corners or sharp edges.

Notably, the mid portion diameter is greater than the outer diameter ofthe underlying tubing 56 of the distal assembly so that a reservoir orannular gap G exists around the exterior of the tubing 56. The gap Gprovides improved fluid distribution from the third lumen 59 to theexterior of the AR electrode via an opening 68 provided in the outerwall of the tubing 56 and apertures 69 strategically formed andpositioned in the side wall 65 of the AR electrode. The size of theopening 68 in the tubing 56 varies with the position along the length ofthe proximal loop 17P. For optimum flow, the more distal an opening isalong the helical form, the greater the size or cross-section of theopening and/or the plurality of openings for each AR electrode.

The apertures 69 are arranged the side wall 65 of an AR electrode in apredetermined pattern including axially offset rows. These aperturesface outwardly promoting flow in a radial direction. Apertures are alsoprovided in or near the curved transitional regions 67 to promote flowin an axial direction. Moreover, these apertures are particularlyeffective in minimizing charring and coagulation at or near the curvedtransitional regions which are likely to be “hot spots” resulting fromhigher current densities due to transitions in the electrode profile. Inthat regard, the plurality and/or cross-section of the apertures isgreater at or near the curved transitional regions than in the side wallof the electrode so as to provide more cooling in the curvedtransitional regions. As such, the catheter can deliver more irrigationand consequently more cooling without increasing overall flow rate andoverall fluid load on the patient.

In some embodiments, there are about 10 apertures on each end portion 66and about 20 apertures on the side wall 65. The pattern may be adjustedto further improve the flow distribution from each AR electrode. Thepattern can be adjusted by adding or removing apertures, modifying thespacing between the apertures, modifying the location of the apertureson the ring electrodes and/or modifying the aperture geometry. Othersuitable ring electrodes are described in the aforementioned U.S. Pat.No. 8,475,450, issued Jul. 2, 1013.

Irrigation fluid is delivered to the distal assembly 17 by theirrigation tubing 43 whose proximal end is attached to a luer hub (notshown) proximal of the control handle 16 and receives fluid delivered bya pump (not shown). The irrigation tubing extends through the controlhandle 16, the central lumen 18 of the catheter body 12, the secondlumen 34 of the intermediate section 14, the central lumen of thetransitional section 20 and a short distance distally into the thirdlumen 59 of the proximal loop 17P, for example, about 5 mm. The fluidenters the third lumen 59 where it exits the lumen via the openings 68into the reservoir R of the AR electrodes where it exits the reservoirvia the apertures 69 to outside of the AR electrodes to minimizecharring.

The number of AR electrodes on the proximal loop 17P can vary asdesired. Preferably the number of AR electrodes ranges from about six toabout twenty, more preferably from about eight to about twelve. In someembodiments, the proximal loop 17P carries ten AR electrodes. Theelectrodes can be approximately evenly spaced around the proximal loop17P, as shown in FIG. 7.

The proximal end of each wire is electrically connected to a suitableconnector (not shown) distal of the control handle 16 for transmittingand/or receiving electrical signals to accomplish ablation. Each ARelectrode is connected to a respective pair of wires 40, 41. In thedisclosed embodiment, wire 40 of the wire pair is a copper wire, e.g. anumber “40” copper wire. The other wire 41 of the wire pair is aconstantan wire. The wires of each pair are electrically isolated fromeach other except at their distal ends where they are twisted together,fed through a hole formed in the second lumen 58 of the proximal loop17P, and soldered to their respective AR electrode (FIG. 14). The wirepairs for each electrode extend from the control handle 16, through thecentral lumen 18 of the catheter body 12, the first lumen 33 of theintermediate section 14, the central lumen of the transitional section20, and the second lumen 58 of the proximal loop 17P. Ablation energy,e.g., RF energy, is delivered to the AR electrodes via the wire 40 ofthe wire pairs. However, the wire pairs inclusive of their respectiveconstantan wire can also function as temperature sensors orthermocouples sensing temperature of each AR electrode.

All of the wire pairs pass through one nonconductive protective sheath42 (see FIG. 6), which can be made of any suitable material, e.g.,polyimide, in surrounding relationship therewith. The sheath 42 extendsfrom the control handle 16, the catheter body 12, the intermediatesection 14, the transitional section 20 and into the second lumen 58 ofthe proximal loop 17P, terminating just distal of the junction betweenthe transitional section 20 and the distal assembly 17, for example,about 5 mm into the second lumen 58. The distal end is anchored in thesecond lumen by glue, for example, polyurethane glue or the like.

An alternate electrode arrangement is depicted in FIG. 11. In thisalternate embodiment, distal assembly 17′ has five AR electrodes andincludes additional ring electrodes that are narrower than the ARelectrodes. Such additional ring electrodes may be impedance recording(IR) electrodes that are electrically isolated from each other and theAR electrodes, and are adapted for recording impedance. In someembodiments of the IR electrodes, the length is about 0.75 mm and theinner diameter is about 2.3 mm. The degree of success of mapping and/orablation depends on tissue contact. Thus, tissue contact information isparticularly useful with multi-electrode ablation catheters. Utilizingat least two independent pairs of IR electrodes (a “pair” hereinafterbeing any two electrodes, or preferably two most adjacent electrodes)with various size and spacing allows assessment of tissue contact bycomparing impedance values and ratio at different frequencies/domainsutilizing a single multi-electrode catheter.

The impedance can be further assessed at various frequencies/domains.For example, the ratio of impedance between a pair of IR electrodes anda pair of AR electrodes is used to assess tissue contact in terms ofverifying contact and degree or amount of contact. With such isolatedbi-polar IR electrodes, the catheter is adapted to perform simultaneousablation, mapping (electrogram recording) and assessment of tissuecontact.

The IR electrodes can be located in between each pair of AR electrodesor selected pairs of AR electrodes depending on the geometry of thedistal assembly 17, to provide accurate tissue contact verification viaa comparison of the impedance between a pair of isolated (smaller) IRelectrodes and the impedance between a pair of (larger) AR electrodes.In the illustrated embodiment of FIG. 11, there are two IR electrodesbetween each adjacent pair of AR electrodes, for a total of 2(N−1)plurality of IR electrodes for N plurality of AR electrodes.

In another alternate embodiment as also illustrated in FIG. 7, thedistal assembly 17 includes electrically isolated bi-polar recordingring (“RR”) electrodes located in between the AR electrodes to provideimproved visualization of pulmonary vein (“PV”) potentials. The catheterwith such isolated bio-polar RR electrodes permits simultaneous ablationand electrogram recording without the need to reposition the catheter.To minimize far-field effects or any decrease in visualizationresolution for more precise electrogram recording of PV potentials, thenarrower bi-polar RR electrodes are positioned with a predeterminedspacing in between each pair of AR electrodes or in between selectedpairs of AR electrodes depending upon the geometry of the distalassembly.

As understood by one of ordinary skill in the art, two closely-spaced RRelectrodes allow for more accurate detection of near field PV potentialversus far field atrial signals, which is very important when trying totreat atrial fibrillation. Specifically, the near field PV potentialsare very small signals whereas the atria, located very close to thepulmonary vein, provide much larger signals. Accordingly, even when thedistal assembly 17 is placed in the pulmonary vein, it can be difficultfor the physician to determine whether the signal is a small, closepotential (from the pulmonary vein) or a larger, farther potential (fromthe atria). Closely-spaced bipoles permit the physician to moreaccurately determine whether he is looking at a close signal or a farsignal. Accordingly, by having closely-spaced electrodes, one is able tobetter target the locations of myocardial tissue that have PV potentialsand therefore allows the clinician to deliver therapy to the specifictissue. Moreover, the closely-spaced electrodes allow the physician todetermine the exact anatomical location of the ostium by the electricalsignal.

In some embodiments, a pair of AR electrodes are provided between eachadjacent pairs of AR electrodes. Thus, for an M plurality of ARelectrodes, there are 2(M−1) plurality of RR electrodes. In theillustrated embodiment, the distal assembly 17 carries 10 AR electrodeswith a spacing of approximately 4.0 mm between adjacent AR electrodes.Where the distal assembly 17 also carries IR or RR electrodes, they canhave a spacing of 1.0 mm between each other. Additionally, the distalmost AR electrode can be a different size from the other AR electrodesso as to provide a visually distinguishing signal to the user when thecatheter is being viewed under fluoroscopy. Specifically, because thedistal assembly 17 is generally circular, it can be difficult for theuser to determine the orientation of the helical form 22 and whichelectrodes are placed at a particular location in the heart. By havingone AR electrode, such as the most distal AR electrode, being longer,the user has a reference point when viewing the catheter underfluoroscopy.

For any additional IR or RR electrodes as described above, additionallead wire pairs 40, 41 are provided as appropriate. They extend throughthe second lumen 58 of the distal assembly 17, the central lumen of theconnector tubing 23, the first lumen 33 of the intermediate section 14,the central lumen 18 of the catheter body 12 and into the control handle16.

The deflection puller wire 54 is provided for deflection of theintermediate shaft 14. The deflection wire 54 extends through thecentral lumen 18 of the catheter body 12 and the sixth lumen 38 of theintermediate section 14. It is anchored at its proximal end in thecontrol handle 16, and at its distal end to a location at or near thedistal end of the intermediate section 14 by means of a T-bar 55 (FIGS.6 and 7) that is affixed to the sidewall of the tubing 15 by suitablematerial 49, e.g., polyurethane. The distal end is anchored to thesidewall of the tubing 15 of the intermediate section as is generallydescribed in U.S. Pat. No. 6,371,955, the entire disclosure of which isincorporated herein by reference. The puller wire 54 is made of anysuitable metal, such as stainless steel or Nitinol, and is preferablycoated with Teflon® or the like. The coating imparts lubricity to thepuller wire. The puller wire preferably has a diameter ranging fromabout 0.006 to about 0.010 inch.

A second compression coil 53 is situated within the central lumen 18 ofthe catheter body 12 in surrounding relation to the puller wire 54 (FIG.5B). The second compression coil 53 extends from the proximal end of thecatheter body 12 to at or near the proximal end of the intermediatesection 14. The second compression coil 53 is made of any suitablemetal, preferably stainless steel, and is tightly wound on itself toprovide flexibility, i.e., bending, but to resist compression. The innerdiameter of the second compression coil 53 is preferably slightly largerthan the diameter of the puller wire 54. The Teflon® coating on thepuller wire allows it to slide freely within the second compressioncoil. Within the catheter body 12, the outer surface of the secondcompression coil 53 is covered by a flexible, non-conductive sheath 61,e.g., made of polyimide tubing. The second compression coil 53 isanchored at its proximal end to the outer wall 30 of the catheter body12 by a proximal glue joint and to the intermediate section 14 by adistal glue joint.

Within the sixth lumen 38 of the intermediate section 14, the pullerwire 54 extends through a plastic, preferably Teflon®, puller wiresheath, which prevents the puller wire 54 from cutting into the wall ofthe tubing 15 of the intermediate section 14 when the intermediatesection 14 is deflected.

With reference to FIG. 1, longitudinal movement of the contraction wire44 relative to the catheter body 12, which results in contraction of theproximal loop 17P of the distal assembly 17, is accomplished by suitablemanipulation of the control handle 16. Similarly, longitudinal movementof the deflection wire 54 relative to the catheter body 12, whichresults in deflection of the intermediate section 14, is accomplished bysuitable manipulation of the control handle 16. Suitable control handlesfor manipulating more than one wire are described, for example, in U.S.Pat. Nos. 6,468,260, 6,500,167, and 6,522,933, the disclosures of whichare incorporated herein by reference. Suitable control handles formanipulating lasso-type catheters are described in U.S. application Ser.No. 12/550,307, filed Aug. 28, 2009 (now published as 2011/0054287 A1),and U.S. application Ser. No. 12/550,204, filed Aug. 28, 2009 (nowpublished as 2011/0054446 A1), the entire disclosures of which areincorporated herein by reference.

In some embodiments, the catheter includes a control handle 16 as shownin FIGS. 12 and 13. The control handle 16 includes a deflection controlassembly that has a handle body 74 in which a core 76 is fixedly mountedand a piston 78 is slidably mounted over a distal region of the core 76.The piston 78 has a distal portion that extends outside the handle body.A thumb knob 80 is mounted on the distal portion so that the user canmore easily move the piston longitudinally relative to the core 76 andhandle body 74. The proximal end of the catheter body 12 is fixedlymounted to the distal end of the piston 78. An axial passage 79 isprovided at the distal end of the piston, so that various components,including lead wires 40, 41, contraction wire 44, deflection wire 54,sensor cable 46 and irrigation tubing 43 that extend through thecatheter body 12 can pass into and if appropriate, through the controlhandle. For example, the lead wires 40, 41 can extend out the proximalend of the control handle 16 or can be connected to a connector that isincorporated into the control handle, as is generally known in the art.

The proximal end of the deflection wire 54 enters the control handle 16,and is wrapped around a pulley 82 and anchored to the core 76.Longitudinal movement of the thumb knob 80 and piston 78 distallyrelative to the handle body 74 and core 76 draws the proximal end of thedeflection wire 54 distally. As a result, the deflection wire 54 pullson the side of the intermediate section 14 to which it is anchored,thereby deflecting the intermediate section in that direction. Tostraighten the intermediate section 14, the thumb knob 80 is movedproximally which results in the piston 78 being moved proximally back toits original position relative to the handle body 74 and core 76.

The control handle 16 is also used for longitudinal movement of thecontraction wire 44 by means of a rotational control assembly. In theillustrated embodiment, the rotational control assembly includes a camhandle 71 and a cam receiver 72. By rotating the cam handle in onedirection, the earn receiver is drawn proximally to draw on thecontraction wire 44. By rotating the cam handle in the other direction,the cam receiver is advanced distally to release the contraction wire.For example, where the proximal loop 17P has an original outer diameterof about 35 mm, tightening of the proximal loop 17P by means of thecontraction wire can reduce the outer diameter to about 20 mm. Thecontraction wire 44 extends from the catheter body 12 into the controlhandle 16, through the axial passage in the piston 78 and through thecore 76 to be anchored in an adjuster 75 by which tension on thecontraction wire can be adjusted.

In some embodiments, the position sensor 48 includes a plurality ofsingle axis sensors (“SAS”) carried on the cable 46 that extends throughthe first lumen 57 of the distal assembly 17 (FIG. 2A), where each SASoccupies a known or predetermined position on the proximal loop 17P. Thecable 46 extends proximally from the distal assembly 17 through thecentral lumen of the transitional section 20, the fourth lumen 36 of theintermediate section 14 (FIG. 6), the central lumen 18 of the catheterbody 12, and into the control handle 16. Each SA sensor can bepositioned with a known and equal spacing separating adjacent SASs. Inthe disclosed embodiment, the cable carries three SASs that arepositioned under the distal-most AR electrode, the proximal-most ARelectrode, and a mid AR electrode, for sensing location and/or positionof the proximal loop 17P. Where the distal assembly carries ten ARelectrodes, the SASs are under electrodes AR1, AR5 and AR10 (FIG. 7).The SASs enable the proximal loop 17P to be viewed under mapping systemsmanufactured and sold by Biosense Webster, Inc., including the CARTO,CARTO XP and NOGA mapping systems. Suitable SASs are described in U.S.application Ser. No. 12/982,765, filed Dec. 30, 2010 (now published as2012/0172703 A1), the entire disclosure of which is incorporated hereinby reference.

In an alternative embodiment of the present invention as illustrated inFIG. 11, distal assembly 17′ includes an electrode-carrying proximalloop 17P′ of which only a portion thereof (e.g., the distalsemi-circular portion of loop 17P′) carries AR electrodes 19. Theproximal loop 17P′ has generally the same structure and construction asthe proximal loop 17P, but the electrode-carrying portion thereofsubtends an angle no greater than about 180 degrees. The distal assembly17′ is particularly useful where the patient has a larger PV ostium orwhere two PV are in such close proximity to each other that they share acommon ostium.

The present catheter 10 is a steerable, multi-electrode, irrigatedluminal catheter. The catheter is deployed in a target region of thebody, e.g., the atria of the heart, through a guiding sheath. Thecatheter is designed to facilitate electrophysiological mapping of thetarget region, e.g., the atria, and to transmit energy, e.g.,radiofrequency (RF) current, to the catheter electrodes for ablationpurposes. For ablation, the catheter is used in conjunction with amulti-channel RF generator and irrigation pump.

The configuration of the catheter permits the catheter to sit at anopening of a tubular formation, e.g., the PV ostia, with consistentcircumferential contact with the tissue. Intracardia signals arerecorded by an EP Recording System and the location of the catheter isvisualized by fluoroscopy. Once the catheter is in the desired location,energy is delivered (to multiple electrodes simultaneously orselectively) to the veins ostium in unipolar or bipolar mode resultingin PV isolation.

In some embodiments, ablation is delivered at a set wattage on themulti-channel RF generator. During ablation the multi-channel RFgenerator monitors the temperature of the ring electrode(s) involved andreduces the wattage if the temperature exceeds a value set by the user.The multi-channel RF generator routes the RF current through theselected ring electrodes and catheter temperature information is sentfrom the thermocouple on the catheter to the generator.

During ablation, an irrigation pump is used to deliver normalheparinized saline to the ring electrodes to cool the ring electrodes toprevent blood from coagulating. The apertures in the ring electrodesfacilitate irrigation of the ablation areas of the catheter. Wheredeeper lesions are desired, the greater flow distribution (withoutgreater flow rate) of each ring electrode via the apertures reduces theincreased risk of charring and coagulum on the ablation surfaces thatwould normally be encountered when the amount of power delivered to theelectrode/tissue interface is increased. A greater flow distributionfrom each ring electrode which leads to improved irrigation efficiencyoffers advantages, including (1) higher power delivery withoutincreasing fluid pump flow rate, (2) ability to use currently available,flow rate-limited pumps, (3) eliminate need to use multiple pumps,and/or (4) reduction in fluid load on patient during ablation procedure.

FIG. 16 illustrates a distal assembly 117 in accordance with anotherembodiment of the present invention. The distal assembly 117 hasgenerally the same structure and construction as the above-describeddistal assembly 17 but soft distal loop 117D provide diagnosticcapabilities by carrying a plurality of ring electrodes 120 adapted forunipolar and/or bipolar sensing of electrical potentials for electrogramrecording without the need to reposition the catheter. Properly spaced,narrow recording electrodes 120 on the distal loop allows for precisevisualization of electrical potentials within the tubular region. Theplurality of ring electrodes 120 ranges between about 10 to 40,preferably about 14 to 30, and more preferably about 20. Accordingly,the distal assembly 117 is particularly useful for the treatment ofatrial fibrillation where, for example, errant electrical activityenters the left atrium from a pulmonary vein, and the distal loop 117Dmay be safely positioned further in the pulmonary vein to detect thesource of the errant electrical activity while the proximal loop 117Pmay be reliably positioned on the pulmonary vein ostium to ablate andblock the errant electrical activity from entering the left atrium. Itis understood that the tubing of the distal assembly 117 may bemulti-lumened, with at least one lumen dedicated to the lead wires ofthe ring electrodes 120 of the distal loop 117D.

FIG. 14 is a schematic pictorial illustration of a system S for ablationof tissue in a heart 126 of a patient 128, in accordance with anembodiment of the present invention. An operator 122, such as acardiologist, inserts a catheter 10 through the vascular system of thepatient so that the distal end of the catheter enters a chamber of thepatient's heart. Operator advances the catheter so that distal assembly17 of the catheter engages endocardial tissue at a desired location orlocations. Catheter 10 is connected by a suitable connector at itsproximal end to a console 130. The console comprises an RF generator forapplying RF energy through electrodes on the end section of the catheterin order to ablate the tissue contacted by the distal section.Alternatively or additionally, catheter may be used for other diagnosticand/or therapeutic functions, such as intracardiac electrical mapping orother types of ablation therapy.

In the pictured embodiment, system S uses magnetic position sensing todetermine position coordinates of the distal assembly of the catheterinside heart. To determine the position coordinates, a driver circuit134 in console 130 drives field generators 132 to generate magneticfields within the body of patient. Typically, field generators comprisecoils, which are placed below the patient's torso at known positionsexternal to the body. These coils generate magnetic fields in apredetermined working volume that contains heart. One or more magneticfield sensors within the end section of catheter generate electricalsignals in response to these magnetic fields. The console 130 processesthese signals in order to determine the position (location and/ororientation) coordinates of the distal assembly 17 of the catheter, andpossibly also the deformation of the distal assembly, as explainedbelow. Console may use the coordinates in driving a display 138 to showthe location and status of the catheter. This method of position sensingand processing is described in detail, for example, in PCT InternationalPublication WO 96/05768, whose entire disclosure is incorporated hereinby reference, and is implemented in the CARTO system produced byBiosense Webster Inc. (Diamond Bar, Calif.).

Alternatively or additionally, system may comprise an automatedmechanism (not shown) for maneuvering and operating catheter within thebody of patient. Such mechanisms are typically capable of controllingboth the longitudinal motion (advance/retract) and the rotation ofcatheter. In such embodiments, console generates a control input forcontrolling the motion of the catheter based on the signals provided bythe position sensing system.

Although FIG. 14 shows a particular system configuration, other systemconfigurations may be used in alternative embodiments of the presentinvention. For example, the methods described hereinbelow may be appliedusing position transducers of other types, such as impedance-based orultrasonic position sensors. The term “position transducer” as usedherein refers to an element mounted on or in catheter that causesconsole to receive signals indicative of the coordinates of the element.The position transducer may thus comprise a received in the catheter,which generates a position signal to the control unit based on energyreceived by the transducer; or it may comprise a transmitter, emittingenergy that is sensed by a receiver external to the probe. Furthermore,the methods described hereinbelow may similarly be applied in mappingand measurement applications using not only catheters, but also probesof other types, both in the heart and in other body organs and regions.

FIG. 15 is a schematic sectional view of heart 126, showing insertion ofcatheter 10 into the heart, in accordance with an embodiment of thepresent invention. To insert the catheter in the pictured embodiment,the operator first passes a guiding sheath 140 percutaneously throughthe vascular system and into right atrium 144 of the heart throughascending vena cava 142. The sheath penetrates through interatrialseptum 148, typically via the fossa ovalis, into left atrium 146.Alternatively, other approach paths may be used. Catheter is theninserted through the guiding sheath until the distal assembly 17 of thecatheter extends past the distal end of the guiding sheath 140 into theleft atrium 146.

Operator aligns the longitudinal axis of guiding sheath 140 (and ofcatheter) inside left atrium 146 with the axis of one of pulmonaryveins. He may use the thumb knob 80 of the control handle 16 to deflectthe intermediate section 14 in directing the distal assembly 17 towardthe target ostium. The operator may carry out this alignment using theposition sensing methods described above, along with a pre-acquired mapor image of heart. Alternatively or additionally, the alignment may beperformed under fluoroscopic or other means of visualization. Theoperator advances the catheter toward the target tubular region orpulmonary vein 13 so that the soft distal end 17E first enters thepulmonary vein, followed by the soft distal loop 17D, both of whichguide the positioning and placement of the electrode-carrying proximalloop 17P onto the ostium (FIG. 4A). The operator may apply a force F inthe axial direction to press the proximal loop 17P onto the ostium toensure contact between the ring electrodes 19 and the tissue (FIG. 4B).Advantageously, the soft distal end 17E and the soft distal loop 17Dpositioned further into the tubular region or pulmonary vein 13 helphold the proximal loop 17P on the ostium so it does not slip off theostium. By manipulating the cam handle 71, the proximal loop 17P iscontracted to fit the PV ostium. In the disclosed embodiment, thecontraction wire 44 is drawn proximally by the cam receiver 72 totighten and decrease the diameter of the proximal loop 17P when the camhandle is turned in one direction. By turning the cam handle in theopposition direction, the cam receiver releases the contraction wire toallow the proximal loop 17P to expand and return to its originaldiameter.

The operator can then rotate the catheter about its axis within theguiding sheath so that the proximal loop 17P traces an annular patharound the inner circumference of the vein. Meanwhile, the operatoractuates RF generator to ablate the tissue in contact with the ARelectrodes along the path. Simultaneously, impedance and/or PV potentialrecordings can be made with the IR and/or RR electrodes. Aftercompleting this procedure around one pulmonary vein, the operator mayshift the sheath and catheter and repeat the procedure around one ormore of the other pulmonary veins.

The preceding description has been presented with reference to presentlypreferred embodiments of the invention. Workers skilled in the art andtechnology to which this invention pertains will appreciate thatalterations and changes in the described structure may be practicedwithout meaningfully departing from the principal, spirit and scope ofthis invention. Any feature or structure disclosed in some embodimentsmay be incorporated in lieu of or in addition to other features of anyother embodiments, as needed or appropriate. As understood by one ofordinary skill in the art, the drawings are not necessarily to scale.Accordingly, the foregoing description should not be read as pertainingonly to the precise structures described and illustrated in theaccompanying drawings, but rather should be read consistent with and assupport to the following claims which are to have their fullest and fairscope.

What is claimed is:
 1. A catheter comprising: an elongated body having alongitudinal axis; a distal assembly distal the elongated body, thedistal assembly having a helical form comprising a proximal loop and adistal loop, and a shape-memory support member extending through atleast the proximal loop; at least one irrigated ablation ring electrodemounted on proximal loop; and a control handle proximal the elongatedbody, wherein the proximal loop has a lesser flexibility and the distalloop has a greater flexibility.
 2. A catheter of claim 1, wherein thehelical loop substends at least about 720 radial degrees.
 3. A catheterof claim 1, wherein the helical loop subtends about 765 radial degrees.4. The catheter of claim 1, wherein the proximal loop subtends about 360radial degrees.
 5. The catheter of claim 1, wherein the distal loopsubtends about 360 radial degrees.
 6. The catheter of claim 1, whereinthe distal assembly includes a generally straight distal end distal ofthe distal loop.
 7. The catheter of claim 6, wherein the generallystraight distal end is on-axis relative a longitudinal axis of thecatheter.
 8. The catheter of claim 1, wherein the proximal loop has agreater radius and the distal loop has a lesser radius.
 9. The catheterof claim 1, wherein the proximal loop and the distal loop are on-axisrelative to a longitudinal axis of the catheter.
 10. The catheter ofclaim 1, wherein the proximal loop and the distal loop are orientedobliquely at an angle relative to a longitudinal axis of the catheter10.
 11. The catheter of claim 10, wherein the oblique angle rangesbetween about 45 degrees to 105 degrees.
 12. The catheter of claim 10,wherein the oblique angle ranges between about 75 to 105 degrees. 13.The catheter of claim 10, wherein the oblique angle is about 90 degrees.14. The catheter of claim 1, wherein the proximal loop includes betweenabout eight to twenty electrodes.
 15. The catheter of claim 1, whereinthe proximal loop includes between about ten electrodes.
 16. Thecatheter of claim 1, wherein the proximal loop includes about sixelectrodes spanning about 180 radial degrees.
 17. The catheter of claim1, further comprising at least one ring electrode adapted to measureimpedance.
 18. The catheter of claim 1, further comprising at least onering electrode adapted to measure PV potentials.
 19. The catheter ofclaim 1, further comprising a contraction wire extending through theelongated body and the distal assembly, wherein the control handleincludes a first control member configured to actuate the contractionwire to contract the helical form.
 20. The catheter of claim 1, furthercomprising a deflection wire extending through the elongated body,wherein the control handle includes a second control member configuredto actuate the deflection wire to deflect a portion of the elongatedbody.